Oxidation of fried sweet potato chips: changes in color, texture, beta-carotene, and headspace volatiles during storage

Abstract: Frying studies with antioxidants and different types of oils often focus on the oxidation and degradation of the oil, but not as much focus has been applied to the effect of different treatments on the shelf-life of food products. Sweet potatoes are a rich source of beta carotene as well as other vitamins, potassium, and fiber. Frying sweet potato chips provides an economical means of dehydrating and preserving the sweet potatoes, and if frying conditions are optimized beta carotene levels can be retained. The objective of this study was to determine markers for shelf-life analysis of fried sweet potato chips, and to evaluate holistically the changes that occur in fried sweet potato chips during storage. Sweet potato chips fried in canola oil were stored at mildly accelerated conditions, 35° C in the dark, and the color, texture, tocopherols, beta-carotene, and headspace volatiles were measured over time. Lipid and beta-carotene oxidation volatiles increased steadily over the first 7 weeks of storage and correlated with a decline in volatiles associated with the sweet potato flavor as well as declines in tocopherol and beta-carotene content. After 7 weeks, lipid oxidation volatiles increased exponentially, together with complete loss of alpha tocopherol and accelerated rates of gamma tocopherol loss, while beta-carotene degradation rate did not appear to change. Color and texture changes were more subtle over time, accompanied by higher measurement variations. Accelerated studies at higher temperatures were also conducted (45°C and 55°C), as well as using a Rancimat to measure induction time at 110 °C. We will discuss how these tools along with others (NIR) can be used to predict and compare shelf-life of sweet potato chips with different oils and antioxidant treatments.